Method for manufacturing glass material and glass material

Abstract

To provide a method for manufacturing a glass material that can acquire a glass material less likely to cause solarization therein.SOLUTION: A method for manufacturing a glass material includes the steps of: providing glass; and heating the glass for six hours or more at (Tg-70)°C or higher and (Tg+40)°C or lower where Tg(°C) represents a glass transition point of the glass material.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a glass material. The present invention also relates to a glass material.

Background Art

[0002] In recent years, research has been conducted on a containerless floating method as a method for manufacturing a glass material. For example, Patent Document 1 describes a method of irradiating a sample of a barium titanate-based ferroelectric material floating in a gas floating furnace with a laser beam, heating and melting it, and then cooling it to vitrify the sample of the barium titanate-based ferroelectric material. Thus, in the containerless floating method, since the progress of crystallization due to contact with the wall surface of the container can be suppressed, there is a case where even a material that could not be vitrified by a conventional manufacturing method using a container can be vitrified. Therefore, the containerless floating method is a method worthy of attention as a method capable of manufacturing a glass material having a novel composition.

[0003] Further, Patent Document 2 discloses a method for manufacturing a glass material by the containerless floating method using, as a glass raw material mass, a mass of crystals obtained by cooling a melt of a raw material batch.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The containerless levitation method allows for the vitrification of materials that were previously difficult to vitrify. However, conventional glass materials produced by the containerless levitation method may undergo solarization (discoloration) when left in bright light, such as under sunlight or fluorescent lights.

[0006] The object of the present invention is to provide a method for manufacturing glass materials that can produce glass materials that are less susceptible to solarization. Another object of the present invention is to provide glass materials that are less susceptible to solarization. [Means for solving the problem]

[0007] The method for manufacturing a glass material according to the present invention is characterized by comprising the steps of: preparing glass; and heat-treating the glass at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more, with Tg (°C) being the glass transition point of the glass.

[0008] In the method for producing glass material according to the present invention, it is preferable that the glass contains, in mol% terms, 50% or more of La2O3+Gd2O3+Y2O3+Yb2O3+Ga2O3+TiO2+ZrO2+Nb2O5+Ta2O5+WO3 and 50% or less of B2O3+SiO2+P2O5+GeO2.

[0009] In the method for producing glass material according to the present invention, it is preferable that the glass contains 10% or more of La2O3 in mol%.

[0010] In the method for manufacturing glass materials according to the present invention, it is preferable that the step of preparing the glass comprises the steps of obtaining molten glass by heating a glass raw material mass while it is suspended in the air, thereby melting the glass raw material mass, and cooling the molten glass to obtain glass.

[0011] The method for manufacturing glass materials according to the present invention is preferably a method for manufacturing glass materials used as optical glass materials.

[0012] The glass material according to the present invention is a glass material containing 50% or more of La2O3 + Gd2O3 + Y2O3 + Yb2O3 + Ga2O3 + TiO2 + ZrO2 + Nb2O5 + Ta2O5 + WO3 and 50% or less of B2O3 + SiO2 + P2O5 + GeO2 in mol%, and the glass material is irradiated with light having a wavelength of 280 nm to 400 nm and an irradiance of 0.1 mW / cm

[0016] ~10 mW / cm 2 for 24 hours to 100 hours, and the first chromaticity b in the L * a * b * a*b* color system of the glass material before light irradiation * and the second chromaticity b in the L * a * b * a*b* color system of the glass material after light irradiation * The absolute value Δb of the difference from * is 0.5 or less.

[0013] The glass material according to the present invention preferably contains 10% or more of La2O3 in mol%.

[0014] The glass material according to the present invention is preferably an optical glass material.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a method for manufacturing a glass material that can obtain a glass material in which solarization hardly occurs. Further, according to the present invention, it is possible to provide a glass material in which solarization hardly occurs.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus for manufacturing glass by a containerless floating method. [Figure 2] FIG. 2 is a diagram showing a first example of a time chart of heating temperatures applicable when heat-treating glass in the present invention. [Figure 3]Figure 3 shows a second example of a heating temperature time chart applicable when heat-treating glass in the present invention. [Figure 4] Figure 4 shows a third example of a heating temperature time chart applicable when heat-treating glass in the present invention. [Figure 5] Figure 5 shows a fourth example of a heating temperature time chart applicable when heat-treating glass in the present invention. [Modes for carrying out the invention]

[0017] Preferred embodiments are described below. However, the following embodiments are merely illustrative, and the present invention is not limited to these embodiments. In addition, in each drawing, components having substantially the same function may be referred to by the same reference numerals.

[0018] (Method of manufacturing glass materials) The method for manufacturing a glass material according to the present invention comprises the steps of preparing glass and heat-treating the glass at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more, with Tg (°C) being the glass transition point of the glass.

[0019] In the containerless levitation method, even compositions that would not vitrify using a container-based melting method can be vitrified. However, conventional glass produced by the containerless levitation method may undergo solarization, such as yellowing, when left in bright light. In contrast, the present invention makes it possible to reduce the likelihood of solarization even in glass produced by the containerless levitation method.

[0020] The glass material manufacturing method according to the present invention can suitably produce, for example, barium titanate glass materials, lanthanum-niobium composite oxide glass materials, lanthanum-tungsten composite oxide glass materials, lanthanum-titanium composite oxide glass materials, lanthanum-tantalum composite oxide glass materials, lanthanum-gallium composite oxide glass materials, lanthanum-aluminum composite oxide glass materials, lanthanum-boron composite oxide glass materials, and the like, and can make it difficult for solarization to occur in such glass materials.

[0021] The present invention's method for manufacturing glass materials is preferably a method for manufacturing glass materials used as optical glass materials (a method for manufacturing optical glass materials).

[0022] <Process for preparing glass> The glass to be prepared is preferably glass manufactured by the containerless flotation method. In this specification, the glass to be prepared may be referred to as "precursor glass". As the glass (precursor glass), for example, conventionally known glass manufactured by the containerless flotation method can be used. The containerless flotation method is a method of obtaining glass by heating a glass raw material mass while it is suspended in the air to obtain molten glass, and then cooling the molten glass.

[0023] In other words, the process of preparing the glass preferably includes the steps of obtaining molten glass by heating the glass raw material mass while it is suspended in the air, thereby melting the glass raw material mass, and cooling the molten glass to obtain glass.

[0024] Figure 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus for producing glass using the containerless levitation method.

[0025] The glass (precursor glass) manufacturing apparatus 1 shown in Figure 1 has a mold 2. The mold 2 has a molding surface 2a and a plurality of gas ejection holes 2b opening into the molding surface 2a. The molding surface 2a is a curved surface. Specifically, the molding surface 2a is spherical. The gas ejection holes 2b are connected to a gas supply mechanism 3 such as a gas cylinder. Gas is supplied from this gas supply mechanism 3 to the molding surface 2a via the gas ejection holes 2b. The type of gas is not particularly limited. Examples of gases include air, oxygen, nitrogen gas, argon gas, helium gas, carbon monoxide gas, and carbon dioxide gas.

[0026] To manufacture glass using the manufacturing apparatus 1, first, gas is ejected from a gas ejection hole 2b that opens into the molding surface 2a of the mold 2, thereby causing the glass raw material mass, which will be the floating object 4, to float on the molding surface 2a. In other words, the glass raw material mass, which will be the floating object 4, is held in a state where it is not in contact with the molding surface 2a.

[0027] Examples of glass raw material ingots include glass raw material powders integrated by press molding, sintered bodies obtained by integrating glass raw material powders by press molding and then sintering them, and aggregates of crystals having a composition equivalent to the target glass composition. Furthermore, the shape of the glass raw material ingot is not particularly limited and can be, for example, lenticular, spherical, cylindrical, polygonal prismatic, rectangular parallelepiped, ellipsoidal, etc.

[0028] Next, with the glass raw material mass (floating object 4) suspended, laser light is irradiated from the laser light irradiation device 5. This heats and melts the glass raw material mass to obtain molten glass. Then, by cooling the molten glass while it is suspended, glass can be obtained.

[0029] The shape and size of the glass are not particularly limited.

[0030] <Heat treatment process> When the glass transition temperature of the above-mentioned glass (precursor glass) is Tg (°C), the glass is heat-treated at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more. Glass produced by the containerless levitation method is generally glass that has a composition that cannot be vitrified by melting methods, etc. Glass produced by the containerless levitation method tends to have a sparse structure. The inventors have found that by heating the glass under the above heat treatment conditions, the structure of the glass becomes denser, and as a result, solarization can be made less likely to occur. Therefore, in the glass material manufacturing method according to the present invention, in addition to glass produced by the containerless levitation method, glass with a sparse structure can also be used as the above-mentioned glass (precursor glass) to suitably produce glass materials that are less prone to solarization.

[0031] The glass transition point of the above-mentioned glass can be measured using a macro-type differential thermal analyzer. Specifically, the value of the first inflection point in the chart obtained by measuring up to 1000°C using a macro-type differential thermal analyzer can be defined as the glass transition point.

[0032] The heating temperature of the glass under the above heat treatment conditions is (Tg-70)°C or higher and (Tg+40)°C or lower, preferably (Tg-50)°C or higher and preferably (Tg+20)°C or lower. If the heating temperature is above the lower limit, the effects of the present invention can be exhibited more effectively and the heat treatment time can be shortened. If the heating temperature is below the upper limit, the effects of the present invention can be exhibited more effectively and the devitrification of the resulting glass material can be effectively suppressed.

[0033] The heating time for the glass under the above heat treatment conditions is 6 hours or more, preferably 9 hours or more, more preferably 12 hours or more, preferably 100 hours or less, and more preferably 30 hours or less. If the heating time is above the lower limit, the effects of the present invention can be exhibited more effectively. If the heating time is below the upper limit, the manufacturing time can be shortened, and devitrification of the resulting glass material can be effectively suppressed.

[0034] The above glass may be heat-treated at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours continuously or for 6 hours or more without continuous heat treatment. In this invention, it is sufficient that the total time the above glass is heat-treated within the temperature range of (Tg-70)°C or higher and (Tg+40)°C or lower is 6 hours or more.

[0035] Figure 2 shows a first example of a heating temperature time chart applicable when heat-treating glass in the present invention.

[0036] In Figure 2, glass is heated at a constant heating rate, held at a constant temperature, and then cooled at a constant cooling rate. In Figure 2, the time when the temperature reached (Tg-70)°C during heating is shown as t1, the time when the temperature reached (Tg-70)°C during cooling is shown as t2, and the time from t1 to t2 is shown as tx. In Figure 2, the time (tx) during which the glass was heat-treated at a temperature between (Tg-70)°C and (Tg+40)°C is 6 hours or more.

[0037] Figure 3 shows a second example of a heating temperature time chart applicable when heat-treating glass in the present invention.

[0038] In Figure 3, glass is heated at a constant heating rate, held at a constant temperature, and then cooled at a constant cooling rate. In Figure 3, the time when the temperature reached (Tg-70)°C during heating is shown as t1, the time when the temperature reached (Tg-70)°C during cooling is shown as t2, and the time from t1 to t2 is shown as tx. In Figure 3, the time the glass is held at a constant temperature is shorter and the cooling rate is slower compared to Figure 2. In Figure 3, the time (tx) during which the glass is heat-treated at a temperature between (Tg-70)°C and (Tg+40)°C is 6 hours or more.

[0039] Figure 4 shows a third example of a heating temperature time chart applicable when heat-treating glass in the present invention.

[0040] In Figure 4, the glass is heated at a constant heating rate (first heating rate), then further heated at a constant heating rate (second heating rate), and then cooled at a constant cooling rate. In Figure 4, the time when the temperature reached (Tg-70)°C during heating is shown as t1, the time when the temperature reached (Tg-70)°C during cooling is shown as t2, and the time from t1 to t2 is shown as tx. In Figure 4, the time (tx) during which the glass was heat-treated at a temperature between (Tg-70)°C and (Tg+40)°C is 6 hours or more.

[0041] Figure 5 shows a fourth example of a heating temperature time chart applicable when heat-treating glass in the present invention.

[0042] In Figure 5, the glass is heated at a constant heating rate (first heating rate), held at a constant temperature, and then cooled at a constant cooling rate (first cooling rate). Next, the glass is held at a constant temperature. Next, the glass is heated at a constant heating rate (second heating rate), held at a constant temperature, and then cooled at a constant cooling rate (second cooling rate). In Figure 5, the time when the temperature reached (Tg-70)°C during the first heating is shown as t1, the time when the temperature reached (Tg-70)°C during the first cooling is shown as t2, the time when the temperature reached (Tg-70)°C during the second heating is shown as t3, and the time when the temperature reached (Tg-70)°C during the second cooling is shown as t4. Also in Figure 5, the time from t1 to t2 is shown as tx1, and the time from t3 to t4 is shown as tx2. In Figure 5, both time (tx1) and time (tx2) are less than 6 hours. In Figure 5, the sum of time (tx1) and time (tx2) is 6 hours or more. Thus, the glass may be heat-treated at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more without continuous heating.

[0043] The above heating rate and cooling rate are not particularly limited. The heating rate can be, for example, 1°C / min or more, preferably 5°C / min or more, 20°C / min or less, and preferably 10°C / min or less. The cooling rate can be, for example, 0.1°C / min or more, preferably 0.13°C / min or more, more preferably 0.15°C / min or more, 10°C / min or less, preferably 5°C / min or less, and more preferably 1°C / min or less.

[0044] The above heat treatment process can be carried out, for example, using an electric furnace under atmospheric conditions.

[0045] (Glass and glass materials) In the method for manufacturing glass materials according to the present invention, the glass (precursor glass) and the glass material according to the present invention preferably contain, in mol% terms, 50% or more of La2O3+Gd2O3+Y2O3+Yb2O3+Ga2O3+TiO2+ZrO2+Nb2O5+Ta2O5+WO3 and 50% or less of B2O3+SiO2+P2O5+GeO2. Conventional glass materials having the above composition are prone to solarization, but in the present invention, even glass materials having the above composition can be made less prone to solarization.

[0046] Typically, the composition of the glass prepared as described above is the same as the composition of the glass material obtained by heat-treating the glass.

[0047] In this specification, unless otherwise specified, in the following descriptions of component content, "%" means "molar percent". Also, in this specification, "x + y + ..." means the sum of the content of each component. Note that the content of at least one of the components in "x + y + ..." may be 0%. Also, in this specification, "~" in numerical ranges means that the numbers listed at both ends are included as the upper and lower limits.

[0048] In this specification, the following preferred types and forms of content of components correspond to the glass prepared in the method for manufacturing the glass material according to the present invention, and to the glass material according to the present invention, respectively.

[0049] The content of La2O3+Gd2O3+Y2O3+Yb2O3+Ga2O3+TiO2+ZrO2+Nb2O5+Ta2O5+WO3 is preferably 50% or more, more preferably 55-100%, even more preferably 60-95%, and particularly preferably 63-90%. In conventional glass materials, solarization is likely to occur if the total content of these components is too high, but in the present invention, solarization can be made less likely to occur even when the total content of these components is high.

[0050] La2O3 is a component that increases the refractive index and enhances the stability of vitrification. The La2O3 content is preferably 10% or more, more preferably 15-70%, even more preferably 20-65%, and particularly preferably 25-63%. If the La2O3 content is too low, it becomes difficult to obtain the above effects. On the other hand, if the La2O3 content is too high, vitrification may become difficult.

[0051] Gd2O3 is also a component that increases the refractive index and enhances the stability of vitrification. The Gd2O3 content is preferably 0-30%, more preferably 5-25%, and even more preferably 10-20%. If the Gd2O3 content is too high, vitrification may become difficult.

[0052] Y2O3 is a component that increases the refractive index. The Y2O3 content is preferably 0-30%, more preferably 1-20%, and even more preferably 5-15%. If the Y2O3 content is too high, vitrification may become difficult.

[0053] Yb2O3 is also a component that increases the refractive index. The Yb2O3 content is preferably 0-20%, more preferably 1-15%, and even more preferably 3-10%. If the Yb2O3 content is too high, devitrification and striations are likely to occur.

[0054] Ga2O3 is a component that enhances glass-forming ability. The Ga2O3 content is preferably 0-50%, more preferably 10-45%, and even more preferably 20-40%. If the Ga2O3 content is too high, devitrification is likely to occur.

[0055] TiO2 is a component that increases the refractive index and also enhances chemical durability. The TiO2 content is preferably 0-86%, more preferably 5-75%, even more preferably 10-50%, and particularly preferably 15-40%. If the TiO2 content is too high, devitrification becomes more likely.

[0056] ZrO2 is a component that enhances refractive index and chemical durability. The ZrO2 content is preferably 0-30%, more preferably 5-20%, and even more preferably 10-18%. Too much ZrO2 content can lead to devitrification.

[0057] Nb2O5 is a component that has a significant effect in increasing the refractive index and also has the effect of broadening the vitrification range. It is also a component that has the effect of lowering the glass transition temperature. The Nb2O5 content is preferably 0 to 80%, more preferably 5 to 70%, and even more preferably 10 to 60%. However, if the Nb2O5 content is too high, vitrification may become difficult.

[0058] Ta2O5 is a component that increases the refractive index. The Ta2O5 content is preferably 0-50%, more preferably 1-45%, and even more preferably 5-40%. If the Ta2O5 content is too high, phase separation and devitrification are likely to occur. Also, since Ta2O5 is a rare and expensive component, a high content of it will increase the raw material cost.

[0059] WO3 is a component that increases the refractive index. The WO3 content is preferably 0-30%, more preferably 1-20%, and even more preferably 5-10%. If the WO3 content is too high, it may absorb light in the visible region and reduce transmittance.

[0060] The content of B2O3+SiO2+P2O5+GeO2 is preferably 0-50%, more preferably 5-45%, even more preferably 10-40%, and particularly preferably 15-37%. When the total content of these components is within the above range, the effects of the present invention can be exhibited even more effectively.

[0061] B2O3 forms the glass skeleton and is a component that has the effect of expanding the vitrification range. It is also a component that has the effect of lowering the glass transition temperature. The B2O3 content is preferably 0 to 50%, more preferably 5 to 40%, and even more preferably 10 to 37%. If the B2O3 content is too high, the refractive index may decrease, making it difficult to obtain the desired optical properties.

[0062] SiO2 forms the glass skeleton and is a component that has the effect of expanding the vitrification range. It is also a component that has the effect of improving weather resistance. The SiO2 content is preferably 0 to 25%, more preferably 5 to 20%, and even more preferably 10 to 15%. If the SiO2 content is too high, the refractive index may decrease, making it difficult to obtain the desired optical properties.

[0063] P2O5 forms the glass skeleton and is a component that has the effect of expanding the vitrification range. The P2O5 content is preferably 0-20%, more preferably 5-10%. If the P2O5 content is too high, phase separation becomes more likely.

[0064] GeO2 is a component that increases the refractive index and also has the effect of broadening the vitrification range. The GeO2 content is preferably 0-20%, more preferably 1-10%, and even more preferably 3-5%. If the GeO2 content is too high, the raw material cost tends to increase.

[0065] Furthermore, the above-mentioned glass and glass material may each contain components other than those described above. Examples of these other components include Al2O3, RO (R: at least one selected from Zn, Mg, Ca, Sr, and Ba), R'2O (R': at least one selected from Li, Na, and K), and RE2O3 (RE: at least one selected from Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, and Lu). These other components may be used individually or in combination of two or more.

[0066] Al2O3 is a component that has the effect of expanding the vitrification range. It is also a component that has the effect of improving weather resistance. The Al2O3 content is preferably 0 to 30%, more preferably 1 to 20%, and even more preferably 5 to 10%. If the Al2O3 content is too high, vitrification may become difficult.

[0067] RO (R: at least one selected from Zn, Mg, Ca, Sr, and Ba) is a component that has the effect of broadening the vitrification range. It is also a component that has the effect of improving weather resistance. The content of each of these components is preferably 0 to 10%, more preferably 0.1 to 5%, and even more preferably 1 to 3%. If the content of these components is too high, the refractive index will decrease, making it difficult to obtain the desired optical properties.

[0068] R'2O (R': at least one selected from Li, Na, and K) is a component that lowers the melting point of the glass and broadens the vitrification range. The content of each of these components is preferably 0-10%, more preferably 1-5%. If the content of these components is too high, the weather resistance will decrease, or the refractive index will decrease, making it difficult to obtain the desired optical properties.

[0069] RE2O3 (RE: at least one selected from Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, and Lu) is a component that increases the refractive index. The content of each of these components is preferably 0-1%, more preferably 0-0.5%. If the content of these components is too high, vitrification becomes difficult.

[0070] The glass material according to the present invention has a wavelength of 280 nm to 400 nm and an irradiance of 0.1 mW / cm². 2 ~10mW / cm 2 When the above glass material is irradiated with light for 24 to 100 hours, the L of the glass material before light irradiation * a * b * chromaticity b in a color system * (First chromaticity b * ) and the L of the above glass material after light irradiation * a * b * chromaticity b in a color system * (Second chromaticity b) * The absolute value of the difference between ) and Δb * However, it is preferable that it be 0.5 or less.

[0071] The above light irradiation conditions apply to the glass material: wavelength 310nm~380nm and irradiance 0.1mW / cm². 2 ~1mW / cm 2 It is preferable that the light is irradiated for 24 to 100 hours. The above light irradiation conditions involve irradiating the glass material with a central wavelength of 313 nm and an irradiance of 0.3 mW / cm². 2 Light, with a central wavelength of 365 nm and an irradiance of 0.3 mW / cm². 2 It is more preferable that the light is irradiated for 24 to 100 hours. The above light irradiation conditions involve irradiating the glass material with a central wavelength of 313 nm and an irradiance of 0.3 mW / cm². 2 Light, with a central wavelength of 365 nm and an irradiance of 0.3 mW / cm². 2 It is even more preferable that the light is irradiated for 100 hours. The above-mentioned "center wavelength 313 nm and irradiance 0.3 mW / cm" 2Light, with a central wavelength of 365 nm and an irradiance of 0.3 mW / cm². 2 It is preferable that the above glass material is simultaneously irradiated with the light.

[0072] The shape of the glass material to be irradiated with the above-mentioned light is not particularly limited.

[0073] The above first chromaticity b * and the second chromaticity b * Each of these measures the spectral transmittance of the glass material, and the chromaticity b is calculated from the resulting transmittance curve. * This can be determined by calculating [the formula].

[0074] The above first chromaticity b * and the second chromaticity b mentioned above * The magnitude of the first chromaticity b is not particularly limited, but usually it is the first chromaticity b mentioned above. * The above is the second chromaticity b * It is smaller than that.

[0075] The second chromaticity b mentioned above * Preferably, it is 2.0 or less, more preferably 1.7 or less, even more preferably 1.5 or less, and particularly preferably 1.4 or less.

[0076] The above first chromaticity b * and the second chromaticity b mentioned above * The absolute value of the difference between Δb and * The absolute value of the above difference Δb is preferably 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. * The smaller the value, the better. The absolute value of the above difference is Δb. * The smaller the value, the more effectively solarization can be suppressed.

[0077] The refractive index of the above glass material is preferably 1.8 or higher, more preferably 1.9 or higher, even more preferably 2.0 or higher, preferably 2.4 or lower, and more preferably 2.3 or lower.

[0078] The above refractive index is shown as a measurement for the d-line (587.6 nm) of a helium lamp.

[0079] The glass material according to the present invention can be suitably manufactured by the glass material manufacturing method described above. The glass material according to the present invention is preferably an optical glass material.

[0080] The present invention will be described in more detail below based on specific examples, but the present invention is not limited in any way to the following examples and can be implemented with appropriate modifications without changing the gist of the invention.

[0081] (Examples 1-17 and Comparative Examples 1-11) Tables 1-3 show the composition and results of the glass materials prepared in Examples 1-17 and Comparative Examples 1-11.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] In the examples and comparative examples, the glass materials were prepared as follows.

[0086] First, glass (precursor glass) was produced by containerless levitation using a manufacturing apparatus similar to that shown in Figure 1. Specifically, raw material batches, prepared to achieve the glass compositions listed in Tables 1-3, were melted at 1400°C to 2000°C until homogeneous to obtain molten glass. Next, the obtained molten glass was rapidly cooled to produce glass (precursor glass) with a diameter of approximately 5 mm to 7 mm. The glass transition temperatures (Tg) of the obtained precursor glass are shown in Tables 1-3.

[0087] Next, the obtained precursor glass was heat-treated in an electric furnace under atmospheric conditions as shown in Tables 1-3. In this way, glass material was obtained.

[0088] The obtained glass material L * a * b * chromaticity b in a color system * (First chromaticity b * The following measurements were taken of the obtained glass material using a low-pressure mercury lamp, resulting in a central wavelength of 313 nm and an irradiance of 0.3 mW / cm². 2 UV light, with a central wavelength of 365 nm and an irradiance of 0.3 mW / cm². 2 The glass material was simultaneously irradiated with UV light for 100 hours. In Examples 8 and 9 and Comparative Example 3, the irradiation was performed for 24 hours. The L of the glass material after light irradiation * a * b * chromaticity b in a color system * (Second chromaticity b) * ) was measured.

[0089] Note that the first and second chromaticity b * The spectral transmittance of glass material polished to a thickness of 3 mm ± 0.1 mm was measured, and the obtained transmittance curve was used to determine L * a * b * chromaticity b in a color system * This was determined by calculating the first chromaticity b. * and the second chromaticity b * The absolute value of the difference between Δb and * The following was calculated: Before and after light irradiation, the brightness L * , chromaticity a * and chromaticity b * Of these, chromaticity b * Because chromaticity b changed the most, * The following were used as evaluation criteria for solarization. The results are shown in Tables 1-3.

[0090] As is clear from Tables 1-3, Examples 1-17 were heat-treated at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more, therefore the absolute value of the difference Δb before and after UV light irradiation is... *The value was 0.5 or less. On the other hand, for Comparative Examples 1 to 11, the heat treatment time at temperatures above (Tg-70)°C and below (Tg+40)°C was less than 6 hours, so the absolute value of the difference before and after UV light irradiation was Δb. * It was above 0.5.

[0091] Furthermore, the refractive index (nd) of the glass materials obtained in Example 1 and Comparative Example 1 was measured. The refractive index was measured using a Shimadzu KPR-2000 after bonding the glass material to a 5 mm thick soda plate substrate and performing right-angle polishing. The refractive index was evaluated using the measurement value against the d line (587.6 nm) of a helium lamp. As a result, the refractive index of the glass material obtained in Example 1 was 2.212, and the refractive index of the glass material obtained in Comparative Example 1 was 2.211. It was confirmed that the glass material obtained in Example 1 showed increased refractive index and a denser structure due to heat treatment compared to the glass material obtained in Comparative Example 1. [Explanation of symbols]

[0092] 1…Glass manufacturing equipment 2...Molding mold 2a…molding surface 2b...Gas vent 3…Gas supply mechanism 4…Floating objects 5…Laser light irradiation device

Claims

1. The process of preparing the glass, When the glass transition temperature of the glass is Tg (°C), the glass is heat-treated at a temperature of (Tg-70)°C or higher and (Tg+40)°C or lower for 6 hours or more. Equipped with, The glass contains La in mol% ２ O ３ Contains 10% or more, The process of preparing the aforementioned glass is A step of obtaining molten glass by heating a glass raw material mass while it is suspended in the air, A step of cooling the molten glass to obtain glass, A method for manufacturing glass materials, comprising the following features.

2. The glass contains, in mol%, La ２ O ３ + Gd ２ O ３ + Y ２ O ３ + Yb ２ O ３ + Ga ２ O ３ + TiO ２ + ZrO ２ + Nb ２ O ５ + Ta ２ O ５ + WO ３ at 50% or more and B ２ O ３ + SiO ２ + P ２ O ５ + GeO ２ at 50% or less, a method for producing the glass material according to claim 1.

3. A method for manufacturing a glass material used as an optical glass material, as described in claim 1 or 2.

4. In mole percent, La ２ O ３ 25% or more, La ２ O ３ +Gd ２ O ３ +Y ２ O ３ +Yb ２ O ３ +Ga ２ O ３ +TiO ２ +ZrO ２ +Nb ２ O ５ +Ta ２ O ５ +WO ３ 50% or more and B ２ O ３ +SiO ２ +P ２ O ５ +GeO ２ Glass material containing 50% or less, The aforementioned glass material has a wavelength of 280 nm to 400 nm and an irradiance of 0.1 mW / cm ２ ~10 mW / cm ２ When the glass material is irradiated with light for 24 to 100 hours, ＊ a ＊ b ＊ The first chromaticity b in a color system ＊ And the L of the glass material after light irradiation ＊ a ＊ b ＊ The second chromaticity b in a color system ＊ The absolute value of the difference between Δb and ＊ However, it is 0.5 or less, and is an optical glass material, a glass material.

Images